VIPERS-like mock catalogs
This WEB page details the steps to produce mocks VIPERS-like catalogs, mimicking real VIPERS observations. These realistic mocks reproduce both the color selection and its effects on the redshift distribution of observed data, and the biases in slit positioning introduced by SSPOC, the slit positioning software, and its effects on the Ra-Dec distribution of the observed data.
The starting catalogs were the first five 7X1 sq degs catalogs listed in the VIPERS section of the Virgo Millennium Database web pages (VIPERS_001 to VIPERS_005) - see this website for more informations.
The cosmology adopted in the simulations is Ωm = 0.25, ΩΛ= 0.75, Ωb = 0.045, h = 0.73, σ8 =0.9, n=1.
From these 5 catalogs we obtained 10 catalogs limited to 22.5 in i-band (AB, CFHTLS) magnitude (the same limit adopted for our VIPERS observations) and applying an offset to their Ra-Dec coordinates to position them at the centers of the observed W1 and W4 fields. These 10 catalogs are listed in the first column of the Table at the end of this web page.
Notice that catalogs differing only for the string W1/W4 in their name contain the same set of simulated galaxies, but offset in their Ra-Dec coordinates to position then in the areas of the observed W1 and W4 fields.
Each file contains for each galaxy an ID number, Ra, Dec, apparent redshift (cosmological+peculiar motions), i-band observed AB CFHTLS magnitude, b-band rest frame magnitude (AB, dust included).
No error in redshift measurement was added to the apparent redshift, as the error estimate is still uncertain (approx 135 km/sec at z~0, as obtained from repeated measurements of objects in our survey, see this plot).
From now onwards we will call these catalogs: complete 22.5 mock catalogs.
These complete catalogs need to be trimmed in redshift in order to obtain the correct parent mock catalogs for our observations.
Vipers observational strategy includes a color cut intended to remove galaxies located at redshift z< 0.5 from the targets catalog. In practice this color cut translates in a redshift distribution for the observed sample that shows a smooth edge around z ~ 0.5, not mimicked by simply cutting the complete 22.5 mock catalogs at z >= 0.5 (see Figure 1).
The mock catalogs to be used as input for SPOC need to reproduce this smoother selection function around z ~ 0.5. The simplest approach is to use just a linear fit to the ratio between the redshift distribution of the observed data and that of the complete 22.5 mock catalogs (this last one normalized in absolute numbers to the observed data in the redshift range 0.6-1.0). Figure 2 shows this fit (orange line in Bottom panel). Error bars on the ratio points are poissonian.
At z > 1 the ratio between the redshift distribution of the observed data and that of the complete 22.5 mock catalogs is consistently lower than 1 (although slightly), possibly a result of our lower success rate in redshift measurements at these redshifts (see also Figure 3).
Applying the results of the linear fit to modify the redshift distribution of the complete 22.5 mock catalogs one obtains the results shown in Figure 4, where the two normalized redshift distributions are virtually indistinguishable up to redshift z ~ 1.
From now onwards we will call these catalogs parent 22.5 mock catalogs. They are listed in the second column of the Table at the end of this web page.
From each 22.5
parent mock catalog we then extracted an observed
galaxy catalog by
applying SPOC. The real data (see Figure 5) display in Ra-Dec the
obvious pattern of the VIMOS quadrants and (less noticeable but still
present) a pattern due to the slit positioning software SPOC. We
reproduced both these patterns applying SPOC to our parent 22.5 mock
catalogs, for a total of 33 pointings for field W1 and 31 pointings
for field W4 - the number of pointings observed in these two fields
as of Jul 2010 (here
are the lists used for W1 and for W4). From
the output SPOC catalogues we further removed 3 galaxies for each
mask (12 galaxies per pointing) to take into account the holes used
for the centering. However we did not remove any further galaxy to
take into account the actual success rate in redshift measurements.
We will call these catalogs the observed VIPERS-like mock catalogs (see the third column of the Table at the end of this web page).
In the following table one can find, for each complete 22.5 mock catalog listed in the Table at the top of this page, the links to the corresponding parent 22.5 mock catalog, and to the observed Vipers-like mock catalog. The header of all these files is always the same (see here).
At these links you may download the total tar files:
W1_cats.tar.gz, W4_cats.tar.gz, W1_cut_cats.tar.gz, W4_cut_cats.tar.gz, W1_Jul2010_cats.tar.gz, W4_Jul2010_cats.tar.gz.
To obtain fully realistic Vipers-like mock catalog one still needs to add to the catalogs of the third column:
a realistic error in redshift measurements, extracted from a gaussian of sigma =135(1+z)km/sec, where z is the redshift of the galaxy considered (see this plot, obtained from repeated measurements of objects in our survey, using summer 2011 data);
a redshift measurement success rate
a masking according to both spectroscopic and photometric masks
Notice also that catalogs with the same three digit order number are not independent (eg. VIPERS_001_22.5_W1.cat and VIPERS_001_22.5_W4.cat).
For those interested here are fifty files (corresp_VIPERS_001.cat, corresp_VIPERS_002.cat, corresp_VIPERS_003.cat, corresp_VIPERS_004.cat, corresp_VIPERS_005.cat, corresp_VIPERS_006.cat, corresp_VIPERS_007.cat, corresp_VIPERS_008.cat, corresp_VIPERS_009.cat, corresp_VIPERS_010.cat, corresp_VIPERS_011.cat, corresp_VIPERS_012.cat, corresp_VIPERS_013.cat, corresp_VIPERS_014.cat, corresp_VIPERS_015.cat, corresp_VIPERS_016.cat, corresp_VIPERS_017.cat, corresp_VIPERS_018.cat, corresp_VIPERS_019.cat, corresp_VIPERS_020.cat, corresp_VIPERS_021.cat, corresp_VIPERS_022.cat, corresp_VIPERS_023.cat, corresp_VIPERS_024.cat, corresp_VIPERS_025.cat, corresp_VIPERS_026.cat, corresp_VIPERS_027.cat, corresp_VIPERS_028.cat, corresp_VIPERS_029.cat, corresp_VIPERS_030.cat, corresp_VIPERS_031.cat, corresp_VIPERS_032.cat, corresp_VIPERS_033.cat, corresp_VIPERS_034.cat, corresp_VIPERS_035.cat, corresp_VIPERS_036.cat, corresp_VIPERS_037.cat, corresp_VIPERS_038.cat, corresp_VIPERS_039.cat, corresp_VIPERS_040.cat, corresp_VIPERS_041.cat, corresp_VIPERS_042.cat, corresp_VIPERS_043.cat, corresp_VIPERS_044.cat, corresp_VIPERS_045.cat, corresp_VIPERS_046.cat, corresp_VIPERS_047.cat, corresp_VIPERS_048.cat, corresp_VIPERS_049.cat, corresp_VIPERS_050.cat) containing the correspondence between the galaxy IDs quoted in our catalogs and the original galaxy IDs of the mocks in the VIPERS section of the Virgo Millennium Database web pages (VIPERS_001 to VIPERS_050). This original ID number can be used to retrieve from the Virgo Millennium Database any further info desired for each galaxy in our mocks.
Here *pointing info tar file* is a tar file containing for each observed galaxy in these 50 mocks the Pointing and the Quadrant of its VIMOS simulated observations.